/platform/frameworks/base: Fixing setFrontOfTask Issue

Issue: The previous task activity appears momentarily
       before the vpn activity exits to home

Fix: Ensure frontOfTask is set in the setFrontOfTask
     function of TaskRecord.java

CRs-Fixed: 713644

Change-Id: Ied88deb6a3243f2593e3533faf1f73ee036129a6